US5095239A - Varistor in an electric motor - Google Patents

Varistor in an electric motor Download PDF

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Publication number
US5095239A
US5095239A US07/436,198 US43619889A US5095239A US 5095239 A US5095239 A US 5095239A US 43619889 A US43619889 A US 43619889A US 5095239 A US5095239 A US 5095239A
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US
United States
Prior art keywords
varistor
commutator
heat sink
motor
annular
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US07/436,198
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English (en)
Inventor
Patrick S. Wang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Johnson Electric SA
Original Assignee
Johnson Electric SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Johnson Electric SA filed Critical Johnson Electric SA
Assigned to JOHNSON ELECTRIC S.A., A CORP. OF SWITZERLAND reassignment JOHNSON ELECTRIC S.A., A CORP. OF SWITZERLAND ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: WANG, PATRICK SHUI-CHUNG
Application granted granted Critical
Publication of US5095239A publication Critical patent/US5095239A/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
    • H02K11/02—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for suppression of electromagnetic interference
    • H02K11/028—Suppressors associated with the rotor

Definitions

  • the present invention relates to a varistor in an electric motor, particularly a fractional horsepower permanent magnet direct current (PMDC) motor.
  • PMDC permanent magnet direct current
  • a varistor may be electrically connected across the commutator segments of the motor.
  • the properties of a varistor may be described by its E1 and E10 levels.
  • the E1 level is the voltage at which 1 milliamp is conducted and the E10 that at which 10 milliamps are conducted.
  • the E1 and E10 levels are temperature dependent and will drop as the varistor temperature rises.
  • For efficient operation of the motor it is necessary to have stable E1 and E10 levels, and in particular to keep the E10 level above the normal operating voltage of the motor otherwise too much current will be shunted through the varistor.
  • Many small PMDC motors are used in high temperature environments, typically 80 degrees centigrade, and so the temperature stability of the varistor becomes particularly important. Also, under stall conditions a high current passes through the motor and localised heating at the commutator will heat up the varistor. If the varistor is not able to dissipate heat fast enough it may overheat and eventually crack or explode.
  • the present invention provides a varistor in a permanent magnet direct current electric motor, wherein the varistor has a heat sink attached thereto.
  • the varistor is annular and the heat sink is attached to an end face of the varistor.
  • the heat sink carries a fan blade.
  • FIG. 1 is a perspective view of a fractional horsepower PMDC motor embodying the invention
  • FIG. 2 is a perspective view on an enlarged scale of a varistor in accordance with the invention.
  • FIG. 3 is a side view of the varistor of FIG. 2 mounted on a commutator of the fractional horsepower PMDC motor of FIG. 1.
  • FIG. 1 shows a fractional horsepower PMDC motor of the type comprising a deep drawn can-like steel casing 20 having a plastics end cap 22 which carries motor brushgear (not shown) for delivering current to a commutator 24 from power input terminals 26.
  • a motor shaft 28 runs in bearings (not shown) in the nd cap 22 and a closed end of the casing 20.
  • Shaft 28 carries the commutator 24 and an armature (not shown).
  • Permanent magnets (not shown) are carried by the casing 20 and form the motor stator.
  • a varistor 30 in accordance with the invention comprises an annular ring 32 of varistor material, that is material whose resistance varies with voltage, which ring has an annular heat sink 34 mounted on a rear face 36.
  • the heat sink 34 extends beyond the outer periphery of the annular ring 32 and has a plurality of fan blades 38 on its surface 40, which abuts the ring 32, radially outwardly of the ring 32.
  • the heat sink 34 is bonded to the ring 32 by adhesive and is formed of a material having a high thermal capacity and good heat conductance properties, typically it will be of metal.
  • the ring 32 carries a plurality of silver pads 42 on its front face 44 for connection to tangs 46 of the commutator 24 (FIG. 2).
  • the rear face 36 may be coated with silver or other conductive material to provide a capacitance between the tangs 46.
  • the heat sink 34 may be of electrically conductive material which is bonded direct to the silvered face 36. Where the face is not silvered, the heat sink 34 is preferably insulated from the varistor ring 2 and may be, for example, of anodised aluminium.
  • the heat sink 34 increases the thermal capacity of the varistor and so slows down the temperature rise of the varistor under stall conditions as well as providing a greater area for heat dissipation. Under running conditions the heat sink 34 and particularly the fan blades 38 enhance the heat dissipation from the varistor ring.
  • the ring 32 is attached to tangs 46 of the segments 48 of commutator 24 in the usual way by soldering.
  • the tangs 46 are supported on a collar 50 of a base of the commutator 24.
  • the tangs 46 are forged to armature wire 52 of the motor armature (not shown) which is mounted on the shaft 28 adjacent the commutator 24.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc Machiner (AREA)
  • Motor Or Generator Cooling System (AREA)
  • Motor Or Generator Current Collectors (AREA)
  • Thermistors And Varistors (AREA)
US07/436,198 1988-11-14 1989-11-14 Varistor in an electric motor Expired - Fee Related US5095239A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8826611 1988-11-14
GB8826611A GB2229571B (en) 1988-11-14 1988-11-14 Varistor for an electric motor

Publications (1)

Publication Number Publication Date
US5095239A true US5095239A (en) 1992-03-10

Family

ID=10646831

Family Applications (1)

Application Number Title Priority Date Filing Date
US07/436,198 Expired - Fee Related US5095239A (en) 1988-11-14 1989-11-14 Varistor in an electric motor

Country Status (5)

Country Link
US (1) US5095239A (fr)
EP (1) EP0369746A3 (fr)
JP (1) JPH02266853A (fr)
GB (1) GB2229571B (fr)
HK (1) HK132494A (fr)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5473212A (en) * 1993-10-13 1995-12-05 Buehler Products, Inc. Varistor disk assembly
US5796203A (en) * 1994-05-11 1998-08-18 Johnson Electric, S.A. Noise suppressed commutator
US5895990A (en) * 1996-07-10 1999-04-20 Johnson Electric S.A. Miniature motor
US5905319A (en) * 1992-01-31 1999-05-18 Mclendon; Martin R. Self inductance bypass motor
US6153960A (en) * 1997-08-12 2000-11-28 Kabushiki Kaisha Sankyo Seiki Seisakusho Small motor with a coil having a continuously wound wire
US6291912B1 (en) * 1997-07-17 2001-09-18 Valeo Climatisation Electric motor, in particular for motor vehicle, with improved cooling radiator
US6362555B1 (en) * 1997-08-12 2002-03-26 Kabushiki Kaisha Sankyo Seiki Seisakusho Small motor with improved connecting structure between coil, riser and varistor
US20040008459A1 (en) * 2002-07-11 2004-01-15 Siemens Westinghouse Power Corporation Protected exciter for an electrical power generator and associated methods
US20040027028A1 (en) * 2002-08-06 2004-02-12 Ho Seung Pun Electric motor
US20070128822A1 (en) * 2005-10-19 2007-06-07 Littlefuse, Inc. Varistor and production method
US20100189882A1 (en) * 2006-09-19 2010-07-29 Littelfuse Ireland Development Company Limited Manufacture of varistors with a passivation layer
US20100284115A1 (en) * 2009-05-05 2010-11-11 Interconnect Portfolio Llc ESD Protection Utilizing Radiated Thermal Relief
US11133720B2 (en) * 2010-06-14 2021-09-28 Black & Decker Inc. Stator assembly for a brushless motor in a power tool
US11811287B2 (en) 2020-06-05 2023-11-07 Milwaukee Electric Tool Corporation Brushless motor for a power tool

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008102524A1 (fr) * 2007-02-19 2008-08-28 Panasonic Corporation Commutateur moulé et moteur à commutateur utilisant celui-ci

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2470096A (en) * 1945-12-12 1949-05-17 Myron Y Eck Commutator
GB629941A (en) * 1944-09-12 1949-09-30 Electrolux Ab Improvements in speed regulating device for electric motors
US3487248A (en) * 1966-02-17 1969-12-30 Victor Company Of Japan Balanced dc motor rotor with spark reducing commutating arrangement
US3488538A (en) * 1967-08-29 1970-01-06 Shigeru Hayashi Spark suppressing arrangement for commutators
US3745505A (en) * 1971-10-21 1973-07-10 J Harnden Semiconductor device-metal oxide varistorheat sink assembly
JPS5336613A (en) * 1976-09-17 1978-04-05 Matsushita Electric Ind Co Ltd Noise eliminator for use in electric motor
JPS53147904A (en) * 1977-05-31 1978-12-23 Matsushita Electric Works Ltd Spark absorbing device for minimotor
GB1547093A (en) * 1976-04-21 1979-06-06 Mabuchi Motor Co Spark quenching device for an electric motor
JPS55106069A (en) * 1979-02-08 1980-08-14 Tdk Corp Noise prevention circuit for micromotor
EP0206980A2 (fr) * 1985-05-22 1986-12-30 Alusuisse-Lonza Services Ag Elément de refroidissement pour dispositifs à semi-conducteur et procédé pour sa fabrication
US4734607A (en) * 1985-11-15 1988-03-29 Mabuchi Motor Co., Ltd. Miniature motor with spark quenching connection between commutator and brushes
US4833357A (en) * 1987-02-27 1989-05-23 Mabuchi Motor Co., Ltd. Rotor for miniature motors
US4859893A (en) * 1987-03-23 1989-08-22 Johnson Electric Industrial Manufactory Limited Commutator with resiliently clamped resistor ring

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3810253A (en) * 1971-08-24 1974-05-07 J Vergara Motor speed control
JPS607904B2 (ja) * 1979-01-23 1985-02-27 ティーディーケイ株式会社 電圧非直線性抵抗素子
JPH0448139Y2 (fr) * 1986-04-15 1992-11-12

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB629941A (en) * 1944-09-12 1949-09-30 Electrolux Ab Improvements in speed regulating device for electric motors
US2470096A (en) * 1945-12-12 1949-05-17 Myron Y Eck Commutator
US3487248A (en) * 1966-02-17 1969-12-30 Victor Company Of Japan Balanced dc motor rotor with spark reducing commutating arrangement
US3488538A (en) * 1967-08-29 1970-01-06 Shigeru Hayashi Spark suppressing arrangement for commutators
US3745505A (en) * 1971-10-21 1973-07-10 J Harnden Semiconductor device-metal oxide varistorheat sink assembly
GB1547093A (en) * 1976-04-21 1979-06-06 Mabuchi Motor Co Spark quenching device for an electric motor
JPS5336613A (en) * 1976-09-17 1978-04-05 Matsushita Electric Ind Co Ltd Noise eliminator for use in electric motor
JPS53147904A (en) * 1977-05-31 1978-12-23 Matsushita Electric Works Ltd Spark absorbing device for minimotor
JPS55106069A (en) * 1979-02-08 1980-08-14 Tdk Corp Noise prevention circuit for micromotor
EP0206980A2 (fr) * 1985-05-22 1986-12-30 Alusuisse-Lonza Services Ag Elément de refroidissement pour dispositifs à semi-conducteur et procédé pour sa fabrication
US4734607A (en) * 1985-11-15 1988-03-29 Mabuchi Motor Co., Ltd. Miniature motor with spark quenching connection between commutator and brushes
US4833357A (en) * 1987-02-27 1989-05-23 Mabuchi Motor Co., Ltd. Rotor for miniature motors
US4859893A (en) * 1987-03-23 1989-08-22 Johnson Electric Industrial Manufactory Limited Commutator with resiliently clamped resistor ring

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5905319A (en) * 1992-01-31 1999-05-18 Mclendon; Martin R. Self inductance bypass motor
US5473212A (en) * 1993-10-13 1995-12-05 Buehler Products, Inc. Varistor disk assembly
US5796203A (en) * 1994-05-11 1998-08-18 Johnson Electric, S.A. Noise suppressed commutator
US5895990A (en) * 1996-07-10 1999-04-20 Johnson Electric S.A. Miniature motor
CN1071509C (zh) * 1996-07-10 2001-09-19 德昌电机股份有限公司 电动机的转子及其制造方法
US6291912B1 (en) * 1997-07-17 2001-09-18 Valeo Climatisation Electric motor, in particular for motor vehicle, with improved cooling radiator
US6153960A (en) * 1997-08-12 2000-11-28 Kabushiki Kaisha Sankyo Seiki Seisakusho Small motor with a coil having a continuously wound wire
US6285109B1 (en) * 1997-08-12 2001-09-04 Kabushiki Kaisha Sankyo Seiki Seisakusho Small motor with improved connecting structure between coil, riser and varistor
US6362555B1 (en) * 1997-08-12 2002-03-26 Kabushiki Kaisha Sankyo Seiki Seisakusho Small motor with improved connecting structure between coil, riser and varistor
US6891706B2 (en) * 2002-07-11 2005-05-10 Siemens Westinghouse Power Corporation Protected exciter for an electrical power generator and associated methods
US20040008459A1 (en) * 2002-07-11 2004-01-15 Siemens Westinghouse Power Corporation Protected exciter for an electrical power generator and associated methods
US20040027028A1 (en) * 2002-08-06 2004-02-12 Ho Seung Pun Electric motor
US6870296B2 (en) * 2002-08-06 2005-03-22 Johnson Electric S.A. Electric motor
CN100397757C (zh) * 2002-08-06 2008-06-25 德昌电机股份有限公司 电动机
US20070128822A1 (en) * 2005-10-19 2007-06-07 Littlefuse, Inc. Varistor and production method
US20100189882A1 (en) * 2006-09-19 2010-07-29 Littelfuse Ireland Development Company Limited Manufacture of varistors with a passivation layer
US20100284115A1 (en) * 2009-05-05 2010-11-11 Interconnect Portfolio Llc ESD Protection Utilizing Radiated Thermal Relief
US8199450B2 (en) * 2009-05-05 2012-06-12 Samsung Electronics Co., Ltd. ESD protection utilizing radiated thermal relief
US11133720B2 (en) * 2010-06-14 2021-09-28 Black & Decker Inc. Stator assembly for a brushless motor in a power tool
US11811287B2 (en) 2020-06-05 2023-11-07 Milwaukee Electric Tool Corporation Brushless motor for a power tool

Also Published As

Publication number Publication date
EP0369746A3 (fr) 1990-12-05
EP0369746A2 (fr) 1990-05-23
HK132494A (en) 1994-12-02
JPH02266853A (ja) 1990-10-31
GB8826611D0 (en) 1988-12-21
GB2229571B (en) 1992-12-23
GB2229571A (en) 1990-09-26

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AS Assignment

Owner name: JOHNSON ELECTRIC S.A., A CORP. OF SWITZERLAND, SWI

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:WANG, PATRICK SHUI-CHUNG;REEL/FRAME:005220/0714

Effective date: 19891215

CC Certificate of correction
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Year of fee payment: 4

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Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

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FP Lapsed due to failure to pay maintenance fee

Effective date: 20000310

STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362